The Ephrata Institute is an intellectual think tank at the outer fringes of the final frontier. Dedicated to the arts and sciences, the Institute seems an unlikely target for an invasion, but it proves easy pickings when the Crusade comes from beyond, determined to impose its harsh, unbending Truth on all the worlds of the Federation. Armed with weaponized gravity, the alien Crusaders will stop at nothing to rescue the universe from its myriad beliefs... even if it means warping the mind and soul of every sentient being they encounter...

Responding to an urgent distress signal, Captain James T. Kirk and the crew of the USS Enterprise soon find themselves in conflict with the Crusade, and facing individual challenges. When Kirk and Spock are transported to the Crusade's distant homeland to confront the source of the invasion, Sulu finds himself trapped behind enemy lines, while Lieutenant Uhura is faced with possibly the most difficult decisions of her career. As the Crusade sets its sights beyond Ephrata IV, it is up to the Enterprise and its besieged crew to keep freedom of thought from being crushed beneath the weight of worlds...